Double-row ball bearing and bearing device for supporting pinion shaft

ABSTRACT

A ball bearing with double raceway rotatably supports a pinion shaft having a pinion gear on its one end. This ball bearing with double raceway is provided with: an outer ring member having a large-diameter raceway surface and a small-diameter raceway surface; an inner ring member having a large-diameter raceway surface and a small-diameter raceway surface that correspond to the large-diameter raceway surface and the small-diameter raceway surface of the outer ring member; a large-diameter-side row of balls that are interpolated between the two large-diameter raceway surfaces; a small-diameter-side row of balls that are interpolated between the two small-diameter raceway surfaces; a large-diameter-side cage that holds the large-diameter-side row of balls; and a small-diameter-side cage that holds the small-diameter-side row of balls. In this ball bearing with double raceway, the row of balls on the anti-pinion gear side of the two rows of balls is subjected to a load prior to the row of balls on the pinion gear side.

FIELD OF THE INVENTION

The present invention relates to a ball bearing with double raceway, andmore particularly concerns the ball bearing with double raceway that isused for rotatably supporting a pinion shaft that is installed in adifferential device in an automobile, a four-wheel-driving-use transferdevice and the like.

BACKGROUND OF THE INVENTION

Referring to FIG. 21, the following description discusses a structure ofa conventional differential device 100. The differential device 100 isprovided with a pinion shaft (drive pinion) 102 placed in itsdifferential case 101, and this pinion shaft 102 has on one axial endthereof a pinion gear 106 that is engaged with a ring gear 108 of adifferential transmission mechanism 107. The pinion shaft 102 issupported so as to freely rotate around its axis by tapered rollerbearings 103 and 104 with single raceway that are placed in a manner soas to separate axially from each other. A companion flange 105, which isconnected to a propeller shaft, not shown, is attached to the otheraxial end of the pinion shaft 102.

In the differential device 100, a bearing device, which rotatablysupports the pinion shaft 102, is constituted by the tapered rollerbearings 103 and 104 that rotatably support the pinion shaft 102 on itshalf way.

In the differential device 100 having such arrangement, since therolling elements of the tapered roller bearings 103 and 104 are rollers,a greater frictional resistance is exerted on the tapered roller bearing103 particularly on the pinion gear 106 side having a greater thrustload. For this reason, the rotary torque becomes greater, resulting indegradation in the efficiency of the differential device 100.

DISCLOSURE OF THE INVENTION

(1) The ball bearing with double raceway of the present invention isused for rotatably supporting a pinion shaft having a pinion gear on itsone end. This bearing is provided with an outer ring member having alarge-diameter raceway surface and a small-diameter raceway surface inan axial direction, an inner ring member that is placed coaxially withthe outer ring and has a large-diameter raceway surface and asmall-diameter raceway surface in the axial direction, which correspondto the large-diameter raceway surface and the small-diameter racewaysurface of the outer ring member, a large-diameter-side row of ballsthat are interpolated between the two large-diameter raceway surfaces, asmall-diameter-side row of balls that are interpolated between the twosmall-diameter raceway surfaces, a large-diameter side cage that holdsthe large-diameter side row of balls, and a small-diameter side cagethat holds the small-diameter side row of balls. In this ball bearingwith double raceway, the internal clearances on the two large-diameterraceway surfaces side as well as on the two small-diameter racewaysurfaces side are designed to have respectively different sizes in sucha manner that upon applying a load on the pinion shaft, the row of ballson the anti-pinion gear side of the two rows of balls is subjected tothe load prior to the row of balls on the pinion gear side.

In the above structure, the rolling elements of the bearing forsupporting the pinion shaft are constituted by a row of balls;therefore, even on the pinion gear side that is subjected to aparticularly great thrust load, a great frictional resistance is notexerted, and the rotary torque is consequently reduced so that, uponapplication of the pinion shaft to a differential device, it becomespossible to prevent a reduction in the efficiency thereof. However, inthe case of a ball bearing with double raceway, the service life of theball bearing with double raceway becomes shorter than that of thetapered ball bearing. For this reason, the inventors of the presentinvention have studied vigorously to find that there is an imbalancedimposed load between the row of balls on the pinion gear side and therow of balls on the anti-pinion gear side, with the result that thesubsequent adverse effect shortens the service life of the two rows ofballs; thus, the present invention has been devised.

In other words, different from a structure in which the ball bearingwith double raceway is simply applied to the pinion shaft, the presentinvention is characterized by a structure in which the internalclearances on the two large-diameter raceway surfaces side as well as onthe two small-diameter raceway surfaces side are designed to haverespectively different sizes in such a manner that upon applying a loadon the pinion shaft, the row of balls on the anti-pinion gear side ofthe two rows of balls is subjected to the load prior to the row of ballson the pinion gear side. With this structure having such features, whena load is applied to the pinion shaft, first, the internal clearance inthe row of balls on the anti-pinion gear side is narrowed so that theload is mainly supported by the row of balls on the anti-pinion gearside, and upon receipt of a higher load, the internal clearance in therow of balls on the pinion gear side is narrowed so that the load isshared between the rows of balls in a manner so as to support the loadby using the row of balls on the pinion gear side. Therefore, theservice lives of the two rows of balls are averaged in a well-balancedmanner so that the service life of the entire bearing is lengthened;thus, when the bearing is applied to the differential device, it becomespossible to provide high efficiency for a long time.

In the present invention, with respect to the internal clearances, theradial internal clearance on the anti-pinion gear side may be madesmaller than the radial internal clearance on the pinion gear side, orthe axial internal clearance on the anti-pinion gear side may be madesmaller than the axial internal clearance on the pinion gear side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing an entire structure of adifferential device according to most preferable embodiment of thepresent invention.

FIG. 2 is an enlarged cross-sectional view that shows an essentialportion of the device.

FIG. 3 is a cross-sectional view that shows a state in which a ballbearing with double raceway is being assembled therein.

FIG. 4 is an enlarged cross-sectional view that shows a radial internalclearance in the ball bearing.

FIG. 5 is a linearized drawing that shows a state in which therespective ball bearings are attached to a pinion shaft.

FIG. 6 is a graph in which the abscissa axis represents the radialinternal clearance and the ordinate axis represents the system servicelife.

FIG. 7 is a cross-sectional view showing an entire structure of adifferential device according to another embodiment of the presentinvention.

FIG. 8 is a cross-sectional view that shows a pinion-shaft-supportingbearing device of the differential device of FIG. 7.

FIG. 9 is an enlarged cross-sectional view that shows thepinion-shaft-supporting bearing device of FIG. 8.

FIG. 10 is a cross-sectional view that shows an axial internal clearanceof the pinion-shaft-supporting bearing device of FIG. 8.

FIG. 11 is a cross-sectional view that shows a unit width of a ballbearing with double raceway of the pinion-shaft-supporting bearingdevice of FIG. 8.

FIG. 12 is a cross-sectional view that shows a unit width of a ballbearing with double raceway of the pinion-shaft-supporting bearingdevice of FIG. 8.

FIG. 13 is a cross-sectional view that shows a state in which a ballbearing with double raceway of the pinion-shaft-supporting bearingdevice is being assembled therein.

FIG. 14 is a cross-sectional view showing an entire structure of adifferential device according to still another embodiment of the presentinvention.

FIG. 15 is a cross-sectional view that shows a pinion-shaft-supportingbearing device of the differential device of FIG. 14.

FIG. 16A is an enlarged cross-sectional view that shows one of sealmembers of the pinion-shaft-supporting bearing device of FIG. 15.

FIG. 16B is an enlarged cross-sectional view that shows the other sealmember of the pinion-shaft-supporting bearing device of FIG. 15.

FIG. 17 is a cross-sectional view showing an entire structure of adifferential device according to still another embodiment of the presentinvention.

FIG. 18 is a cross-sectional view that shows a pinion-shaft-supportingbearing device of the differential device of FIG. 17.

FIG. 19 is a cross-sectional view showing a pinion-shaft-supportingbearing device of a differential device according to still anotherembodiment of the present invention.

FIG. 20 is a cross-sectional view showing a pinion-shaft-supportingbearing device of a differential device according to the otherembodiment of the present invention.

FIG. 21 is a cross-sectional view that shows an entire structure of aprior art differential device.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description discusses a ball bearing with double racewayin accordance with the most preferable embodiment of the presentinvention, when it is applied to a pinion-shaft-supporting bearingdevice in a differential device to be installed in a vehicle.

Here, FIG. 1 is a cross-sectional view showing a schematic structure ofa differential device, FIG. 2 is an enlarged cross-sectional viewthereof, FIG. 3 is a cross-sectional view that shows a state in which aball bearing with double raceway is being assembled therein, FIG. 4 isan enlarged cross-sectional view that shows a radial internal clearancein the ball bearing with double raceway, FIG. 5 is a line drawing thatshows a state in which the respective ball bearings with double race wayare attached to a pinion shaft, and FIG. 6 is a graph in which the axisof abscissas represents the radial internal clearance and the axis ofordinates represents the system service life.

As shown in FIG. 1, a differential device 1 has a differential case 2.This differential case 2 is constituted by a front case 3 and a rearcase 4. The front case 3 and the rear case 4 are attached by bolt andnut 2 a to each other. Annular walls 27A and 27B used for attachingbearings are formed inside the front case 3. The differential case 2 hasa differential transmission mechanism 5 that differentially drives rightand left wheels in corporation with each other and a pinion shaft (drivepinion) 7 having a pinion gear 6 attached to one end thereof, which areinstalled therein. The pinion gear 6 is meshed with a ring gear 8 of thedifferential transmission mechanism 5. The shaft portion 9 of the pinionshaft 7 is formed into a stepped shape with the other end having asmaller diameter than the one end.

The shaft portion 9 of the pinion shaft 7 has its one end rotatablysupported on the annular wall 27A formed on the front case 3 through aball bearing with double raceway 10 around its axis. The shaft portion 9of the pinion shaft 7 has the other end thereof rotatably supported onthe annular wall 27B of the front case 3 through a ball bearing withdouble raceway 25 around its axis.

As shown in FIG. 2, the ball bearing with double raceway 10 isconstituted by an outer ring member 11 having a large-diameter racewaysurface 11 a on the pinion side and a small-diameter raceway surface 11b on the anti-pinion side and a first unit member 21. The first unitmember 21 is attached to the outer ring member 11 in the axial directionfrom the pinion side toward the anti-pinion side. The outer ring member11 is fitted to the inner circumferential face of the annular wall 27A.The outer ring member 11 is prepared as a counter-bored outer ring. Aflat face portion 11 c that has a diameter larger than thesmall-diameter raceway surface 11 b and is continuously connected to thelarge-diameter raceway surface 11 a is formed between the large-diameterraceway surface 11 a and the small-diameter raceway surface 11 b of theouter ring member 11. With this arrangement, the inner circumferentialface of the outer ring member 11 is formed into a stepped shape.

As shown in FIG. 3, the first unit member 21 is constituted by an innerring member 13 having a large-diameter raceway surface 13 a that facesthe large-diameter raceway surface 11 a of the outer ring member 11 inthe radial direction and a small-diameter raceway surface 13 b thatfaces the small-diameter raceway surface 11 b thereof in the radialdirection, and cages 19 and 20 that hold balls 17 and 18 respectivelyconstituting a large-diameter-side row of balls 15 on the pinion sideand a small-diameter-side row of balls 16 on the anti-pinion side.

The inner ring member 13 is prepared as a counter-bored inner ring. Theinner ring member 13 is inserted through the pinion shaft 7. One axialend face of the inner ring member 13 is made in contact with an end faceof the pinion gear 6 in the axial direction. The inner ring member 13 issandwiched in the axial direction, between the end face of the piniongear 6 and a plastic spacer 23 that is externally fitted to the shaftportion 9 of the pinion shaft 7 on its half way, and that is used forsetting a pre-load.

A flat face portion 13 c that has a diameter larger than thesmall-diameter raceway surface 13 b and is continuously connected to thelarge-diameter raceway surface 13 a is formed between the large-diameterraceway surface 13 a and the small-diameter raceway surface 13 b of theinner ring member 13. With this arrangement, the outer circumferentialface of the inner ring member 13 is formed into a stepped shape.

As shown in FIG. 4, the large-diameter-side row of balls 15 is placedbetween the large-diameter raceway surface 11 a and the large-diameterraceway surface 13 a with a predetermined radial internal clearance α1.The small-diameter-side row of balls 16 is placed between thesmall-diameter raceway surface 11 b and the small-diameter racewaysurface 13 b with a predetermined radial internal clearance β1 that issmaller than a radial inner diameter clearance α1.

In the ball bearing with double raceway 10, the diameter of each ball 17of the large-diameter-side row of balls 15 and the diameter of each ball18 of the small-diameter-side row of balls 16 are made equal to eachother. The pitch circle diameters D1 and D2 of the respective rows ofballs 15 and 16 are different from each other. The pitch circle diameterD1 of the large-diameter-side row of balls 15 is made greater than thepitch circle diameter D2 of the small-diameter-side row of balls 16. Theball bearing with double raceway 10 having the rows of balls 15 and 16that have the different pitch circle diameters D1 and D2 is particularlyreferred to as a tandem-type ball bearing with double raceway.

As shown in FIG. 2, the ball bearing with double raceway 25 isconstituted by an outer ring member 12 having a small-diameter racewaysurface 12 a on the pinion side and a large-diameter raceway surface 12b on the anti-pinion side and a second unit member 22. The second unitmember 22 is attached to the outer ring member 12 in the axial directionfrom the anti-pinion side toward the pinion side. In the outer ringmember 12, a flat face portion 12 c that has a diameter larger than thatof the small-diameter raceway surface 12 b and is continuously connectedto the large-diameter raceway surface 12 a is formed between thelarge-diameter raceway surface 12 a and the small-diameter racewaysurface 12 b. With this arrangement, the inner circumferential face ofthe outer ring member 12 of the ball bearing with double raceway 25 isformed into a stepped shape. The outer ring member 12 is fitted to theinner circumferential face of the annular wall 27B. The outer ringmember 12 is prepared as a counter-bored outer ring.

The second unit member 22 is constituted by an inner ring member 14having a small-diameter raceway surface 14 a that faces thesmall-diameter raceway surface 12 a of the outer ring member 12 in theradial direction and a large-diameter raceway surface 14 b that facesthe large-diameter raceway surface 12 b thereof in the radial direction,a small-diameter-side row of balls 28 on the pinion side as well as alarge-diameter-side row of balls 29 on the anti-pinion side, and cages32 and 33 that hold balls 30 and 31 respectively constituting therespective rows of balls 28 and 29 in a manner so as to be evenlydistributed in the circumferential direction. The inner ring member 14is prepared as a counter-bored inner ring. The inner ring member 14 isinserted through the pinion shaft 7, and the inner ring member 14 issandwiched by a plastic spacer 23 used for setting a pre-load and theshielding plate 37 in the axial direction.

A flat face portion 14 c, which has a diameter smaller than that of thelarge-diameter raceway surface 14 b, and is continuously connected tothe small-diameter raceway surface 14 a, is formed between thesmall-diameter raceway face 14 a and the large-diameter raceway surface14 b. With this arrangement, the outer circumferential face of the firstinner ring member 14 is formed into a stepped shape.

As shown in FIG. 4, the small-diameter-side row of balls 28 are placedbetween the small-diameter raceway surface 12 a and the small-diameterraceway surface 14 a with a predetermined radial internal clearance α2.The large-diameter-side row of balls 29 are placed between thelarge-diameter raceway surface 12 b and the large-diameter racewaysurface 14 b with a predetermined radial internal clearance β2 that issmaller than the predetermined radial inner diameter clearance α2.

In the ball bearing with double raceway 25, the diameter of each ball 30of the small-diameter-side row of balls 28 and the diameter of each ball31 of the large-diameter-side row of balls 29 are made equal to eachother. The pitch circle diameters D3 and D4 of the respective rows ofballs 28 and 29 are different from each other. The pitch circle diameterD3 of the small-diameter-side row of balls 28 is made smaller than thepitch circle diameter D4 of the large-diameter-side row of balls 29. Theball bearing with double raceway 25 is also prepared as a tandem-typeball bearing with double raceway.

An oil circulating path 40 is formed between an outer wall and theannular wall 27A of the front case 3. An oil inlet 41 of the oilcirculating path 40 has its opening on the ring gear 8 side of the oilcirculating path 40. An oil outlet 42 of the oil circulating path 40 hasits opening between the annular wall 27A and the annular wall 27B.

The differential device 1 has a companion flange 43. This companionflange 43 has a trunk portion 44 and a flange portion 45 that isintegrally formed with the trunk portion 44. The trunk portion 44 of thecompanion flange 43 is externally attached to the other side of a shaftportion 9 of the pinion shaft 7, that is, the drive shaft side, notshown. A shielding plate 37 is interpolated between one end face 14 ofthe trunk portion 44 of the companion flange 43 and an end face of aninner ring member 14 of a ball bearing with double raceway 25. An oilseal 46 is placed between the outer circumferential face of the trunkportion 44 of the companion flange 43 and the inner circumferential faceof the opening on the other side of the front case 3. A seal protectingcup 47 to be used for covering the oil seal 46 is attached to theopening on the other side of the front case 3. A thread portion 48 isformed on the outer end on the other side of the shaft portion 9. Thethread portion 48 protrudes into a center recessed section 43 a of theflange portion 45. A nut 49 is meshed with the thread portion 48.

The nut 49 is meshed with the thread portion 48 so that the inner ringmembers 13 and 14 of the respective ball bearings with double raceway 10and 25 are sandwiched by the end face of the pinion gear 6 and the endface of the companion flange 43 in the axial direction so that apredetermined pre-load is applied to the ball bearings with doubleraceway 10 and 25 through the shielding plate 37 and a plastic spacer23.

In the differential device 1 having the arrangement, lubricating oil 50is stored inside the differential case 2 so as to be maintained at alevel L in a driving-stop state. The oil 50 is splashed up as the ringgear 8 rotates upon driving so that the oil is directed and suppliedbetween the ball bearings with double raceway 10 and 25 through the oilcirculating path 40 inside the front case 3 to lubricate the ballbearings with double race way 10 and 25, and is again circulated throughthe inside of the differential case 2. This system which lubricates thebearing by circulating the oil 50 through the inside of the differentialcase 2 is referred to as an oil lubricating type.

The following description discusses an assembling method of thedifferential device 1.

Upon assembling the differential device 1, the ball bearing with doubleraceway 10 is preliminarily assembled in such a manner that the radialinternal clearance α1 between the large-diameter-side row of balls 15and the large-diameter raceway surface 11 a of the outer ring member 11as well as the large-diameter raceway surface 13 a of the inner ringmember 13 is adjusted. Moreover, the radial internal clearance β1between the small-diameter-side row of balls 16 and the small-diameterraceway surface 11 b of the outer ring member 11 as well as thesmall-diameter raceway surface 13 b of the inner ring member 13 isadjusted. At this time, the radial internal clearances α1 and β1 arecontrolled so that the radial internal clearance β1 is made smaller thanthe radial internal clearance α1.

Upon assembling the differential device 1, the ball bearing with doubleraceway 25 is preliminarily assembled in such a manner that the radialinternal clearance α2 between the small-diameter-side row of balls 28and the small-diameter raceway surface 12 a of the outer ring member 12as well as the small-diameter raceway surface 14 a of the inner ringmember 14 is adjusted. Moreover, the radial internal clearance β2between the large-diameter-side row of balls 29 and the large-diameterraceway surface 12 b of the outer ring member 12 as well as thelarge-diameter raceway surface 14 b of the inner ring member 14 isadjusted. At this time, the radial internal clearances α2 and β2 arecontrolled so that the radial internal clearance β2 is made smaller thanthe radial internal clearance α2.

Moreover, the respective outer ring members 11 and 12 of the ballbearings with double raceway 10 and 25 are preliminarily press-insertedinto the annular walls 27A and 27B. In a separated manner from thisprocess, the inner ring member 13 of the first unit member 21 of theball bearing with double raceway 10 is inserted through the pinion shaft7 so that the first unit member 21 is positioned on the pinion gear 6side of the shaft portion 9 of the pinion shaft 7.

Next, in a state where the front case 3 and the rear case 4 are stillseparated from each other, the outer ring member 11 of the ball bearingwith double raceway 10 is assembled into the front case 3. At this time,the outer ring member 11 is press-inserted to a predetermined positionin the axial direction at which it comes into contact with the stepportion formed in the annular wall 27A from one end opening of the frontcase 3. Further, the outer ring member 12 of the ball bearing withdouble raceway 25 is press-inserted to a predetermined position in theaxial direction at which it comes into contact with the step portionformed in the annular wall 27B from the other end opening of the frontcase 3.

As described above, the pinion shaft 7 to which the first unit member 21has been attached is inserted from the small diameter side, that is,from the one end opening of the front case 3, so that the balls 18 ofthe small-diameter-side row of balls 16 of the first unit member 21 arefitted to the smaller-diameter raceway surface 11 b of the outer ringmember 11 and the balls 17 of the large-diameter-side row of balls 15 ofthe first unit member 21 are fitted to the large-diameter racewaysurface 11 a of the outer ring member 11.

Next, the plastic spacer 23 is externally fitted and inserted to theshaft portion 9 of the pinion shaft 7 from the other end opening of thefront case 3. Successively, the inner ring member 14 of the second unitmember 22 is inserted and attached to the shaft portion 9 of the pinionshaft 7 from the other end opening of the front case 3.

Thereafter, the shielding plate 37 is inserted to the shaft portion 9 ofthe pinion shaft 7 from the other end opening of the front case 3, andthe oil seal 46 is attached thereto and the seal protective cup 47 isattached to the other end opening of the front case 3 so that the trunkportion 44 of the companion flange 43 is inserted through the sealprotective cup 47 with its end face being made in contact with theshielding plate 37. Successively, the nut 49 is engaged with thethreaded portion 48 of the shaft portion 9. Thus, the balls 17 and 18 ofthe first unit member 21 and the balls 30 and 31 of the second unitmember 22 are respectively subjected to predetermined pre-loads. Sincethe large-diameter-side row of balls 15 and the smaller-diameter-siderow of balls 28 are respectively placed on the pinion side in the ballbearings with double raceway 10 and 25, these are subjected to a greaterload in comparison with the small-diameter-side row of balls 16 and thelarge-diameter-side row of balls 29.

Here, in the case when the large-diameter-side row of balls 15 and thesmall-diameter-side row of balls 16 are respectively indicated by HL andHS, with the small-diameter-side row of balls 28 and thelarge-diameter-side row of balls 29 being respectively indicated by TSand TL, Table 1 shows relationships between the radial internalclearances in the respective rows of balls 15, 16, 28, 29 and the systemlife. TABLE 1 Radial clearance (μm) α1,α2,β1,β2 Rows of balls with Rowsof balls without 0 10 20 pre-load pre-load System life (km) HL  TSHS    TS 26254 23248 20716 HS  TS HL    TL 31915 29411 26531 HS  TLHL    TS 33155 30921 28228  HL  HS 31214 31214 31214  TS  TL

FIG. 6 shows a graph obtained when the radial internal clearances, α1,α2, β1 and β2 (μm), are plotted on the axis of abscissas with the systemlife (km) being plotted on the axis of ordinates. In this figure, solidline a indicates cases in which a pre-load is applied to HL and TL (withno pre-load applied to HS and TS), broken line b indicates cases inwhich a pre-load is applied to HS and TS (with no pre-load applied to HLand TL), two-dot chain line c indicates cases in which a pre-load isapplied to HS and TL (with no pre-load applied to HL and TS), andone-dot chain line d indicates cases in which no pre-load is applied toany of HL, HS, TS and TL.

As shown in Table 1 and FIG. 6, it is found that, when a case in whichno pre-load is applied to any of HL, HS, TS and TL is taken as areference, the case (indicated by the two-dot chain line c) in which apre-load is applied to HS (small-diameter-side row of balls 16) and TL(large-diameter-side row of balls 29) with no pre-load being applied toany of HL (large-diameter-side row of balls 15) and TS(small-diameter-side row of balls 28) provides the longest system life.

As described above, HL and TS correspond to the large-diameter-side rowof balls 15 and the small-diameter-side row of balls 28 located on thepinion side in the respective ball bearings with double raceway 10 and25, and HS and TL correspond to the small-diameter-side row of balls 16and the large-diameter-side row of balls 29 located on the anti-pinionside in the respective ball bearings with double raceway 10 and 25. Whenthe ball bearings with double race way 10 and 25 are applied to thedifferential device 1, HL (the large-diameter-side row of balls 15) andTS (the small-diameter-side row of balls 28) are subjected to severerload conditions in comparison with HS (the small-diameter-side row ofballs 16) and TL (the large-diameter-side row of balls 29). Therefore,by making the radial internal clearances α1 and α2 of thelarge-diameter-side row of balls 15 and the small-diameter-side row ofballs 28 greater than the radial internal clearances β1 and β2 of thesmall-diameter-side row of balls 16 and the large-diameter-side row ofballs 29, the load is first imposed on the small-diameter-side row ofballs 16 and the large-diameter-side row of balls 29 upon receipt of aload on the respective ball bearings with double raceway 10 and 25. Uponreceipt of a greater load, the radial internal clearances α1 and α2 ofthe large-diameter-side row of balls 15 and the small-diameter-side rowof balls 28 are narrowed to receive the load so that the imposed load isthus shared by the large-diameter-side row of balls 15 and thesmall-diameter-side row of balls 28 as well as the small-diameter-siderow of balls 16 and the large-diameter-side row of balls 29. Even whensuch a great load is exerted on the pinion shaft 7, the imposed load isshared by the respective rows of balls 15 and 16 so that the system lifeof each of the ball bearings with double raceway 10 and 25 islengthened, in particular, the life of each of the large-diameter-siderow of balls 15 and the small-diameter-side row of balls 28 islengthened.

Here, Table 1 and FIG. 6 show that, when the values of the radialinternal clearances α1 and α2 reach 20 μm, the system life is shortened.For this reason, the radial internal clearances α1 and α2 are preferablysuppressed to values of 10 μm or less.

Moreover, in this embodiment, with respect to the ball bearing on thepinion gear 6 side that is subjected to a greater load in comparisonwith the anti-pinion 6 side, a ball bearing with double raceway 10 hasmaller frictional resistance is used. With this arrangement, incomparison with a conventional tapered roller bearing, the rotary torqueis reduced, thereby making it possible to improve the efficiency of thedifferential device 1. Moreover, by using not a ball bearing with singleraceway, but a ball bearing with double raceway, the load capacity isincreased in comparison with the ball bearing with single raceway sothat sufficient supporting rigidity is obtained.

In addition, with respect to the ball bearing with double raceway 10, atandem-type ball bearing with double raceway in which the pitch circlediameter D1 of the small-diameter-side row of balls 15 on the piniongear 6 side is made greater than the pitch circle diameter D2 of thelarge-diameter-side row of balls 16 is used so that, when the balls 17and 18 of the two rows have the same diameter, the number of the balls17 on the small-diameter-side row of balls 16 on the pinion gear 6 sideto which a greater load is exerted is increased; thus, the loadsupporting capability required as the bearing is improved.

In the embodiment, the ball bearings with double raceway 10 and 25 areused in the pinion-shaft-supporting bearing device of the differentialdevice 1 of a vehicle. However, the present invention is not limited tothis embodiment. In other words, one of bearing rings, which is aconstituent element of the ball bearing with double raceway, ispreliminarily attached to one of the shaft and the housing, and theother constituent element of the ball bearing with double raceway isassembled to the other of the shaft and the housing, and in thisarrangement, the shaft may be inserted to the housing; thus, the presentinvention can be applied to a device with this arrangement.

In the present invention, with respect to a rolling bearing with doubleraceway, arrangements having three or more rows of balls or a group ofrollers may be used. In these cases also, the radial internal clearancebetween the rolling elements placed on the side subjected to a smallerload and the raceway surface thereof is preferably made smaller than theradial internal clearance between the rolling elements placed on theside subjected to a greater load and the raceway surface thereof.

As is clear from the above explanation, in accordance with the presentinvention, in particular, the lives of the balls in the ball bearingwith double raceway are averaged so that the life of the entire rollingbearing with double raceway can be lengthened.

Another Embodiment

A rolling bearing with double raceway in accordance with anotherembodiment of the present invention is applied to apinion-shaft-supporting bearing device of a differential device, andreferring to FIGS. 7 to 13, the following description discusses thearrangement thereof.

In this embodiment, a ball bearing with single raceway 25 is used inplace of the ball bearing with double raceway 25 in the embodiment shownin FIG. 1. Reference numeral 1 represents a differential device, 2 is adifferential case, 3 is a front case, 4 is a rear case, 2 a is bolt andnut 27A and 27B are annular walls, 5 is a differential transmissionmechanism, 6 is a pinion gear, 7 is a pinion shaft, 8 is a ring gear,and 9 is a shaft portion of the pinion shaft 7. Reference numeral 10represents a tandem-type ball bearing with double raceway, 40 is an oilcirculating path, 41 is an oil inlet, and 42 is an oil outlet.

Referring to FIG. 8, in the same manner as the structure shown in FIG.2, the ball bearing with double raceway 10 is provided with an outerring member 11 having a large-diameter raceway surface 11 a on thepinion gear side and a small-diameter raceway surface 11 b on theanti-pinion gear side, and an inner ring member 13 having alarge-diameter raceway surface 13 a that faces the large-diameterraceway surface 11 a of the outer ring member 11 in the radial directionand a small-diameter raceway surface 13 b that faces the small-diameterraceway surface 11 b thereof in the radial direction, and cages 19 and20 that hold balls 17 and 18 respectively constituting alarge-diameter-side row of balls 15 on the pinion side and asmall-diameter-side row of balls 16 on the anti-pinion side as rollingelements of double raceway in a manner so as to be located at evenlydistributed positions in the circumferential direction.

As shown in FIG. 9, the outer ring member 11 of the ball bearing withdouble raceway 10 is prepared as a counter-bored outer ring. A flat faceportion 11 c, which has a diameter greater than that of thesmall-diameter raceway surface 11 b, and is continuously connected tothe larger-diameter raceway surface 13 a, is formed between thelarge-diameter raceway surface 11 a and the small-diameter racewaysurface 11 b of the outer ring member 11. With this arrangement, theinner circumferential face of the outer ring member 11 is formed into astepped shape.

The inner ring member 13 is prepared as a counter-bored inner ring. Aflat face portion 13 c, which has a diameter greater than that of thesmall-diameter raceway surface 13 b, and is continuously connected tothe larger-diameter raceway surface 13 a, is formed between thelarge-diameter raceway surface 13 a and the small-diameter racewaysurface 13 b of the inner ring member 13. With this arrangement, theouter circumferential face of the inner ring member 13 is formed into astepped shape.

In the ball bearing with double raceway 10, the diameter of each ball 17of the large-diameter-side row of balls 15 and the diameter of each ball18 of the small-diameter-side row of balls 16 are equal to each other.The pitch circle diameters D1 and D2 of the respective rows of balls 15and 16 are different from each other. The pitch circle diameter D1 ofthe large-diameter-side row of balls 15 is made greater than the pitchcircle diameter D2 of the small-diameter-side row of balls 16. The ballbearing with double raceway 10 having the rows of balls 15 and 16 thathave the different pitch circle diameters D1 and D2 is referred to as atandem-type ball bearing with double raceway.

The ball bearing with single raceway 25, which is an angular ballbearing with single raceway, is constituted by an outer ring member 12having an outer ring raceway surface 12 a and an inner ring member 14having an inner ring raceway surface 14 a that faces the outer ringraceway surface 12 a in the radial direction, a row of balls 28 servingas rolling elements of a single raceway, and a cage 32 that holds theballs 30 constituting the row of balls 28 in a circumferential directionin an evenly distributed manner.

Referring to FIG. 10, the following description discusses an axialinternal clearance of the ball bearing with double raceway 10. Forexample, the axial internal clearance refers to an amount of shiftobtained when, while the inner ring member 13 serving as one of theinner and outer ring members is secured, the outer ring member 11serving as the other thereof is shifted in the axial direction. In astate where the small-diameter raceway surface 11 b is made in contactwith the small-diameter-side row of balls 16 by shifting the outer ringmember 11 in the axial direction, a clearance γ appears between thelarge-diameter raceway surface 11 a and the large-diameter-side row ofballs 15.

In other words, the axial internal clearance of the large-diameter-siderow of balls 15 is made greater than the axial internal clearance of thesmall-diameter-side row of balls 16 by the dimension γ.

As shown in FIG. 11, in a state where only the small-diameter-side rowof balls 16 are attached, the outer ring member 11 is shifted in theaxial direction so as to make the small-diameter raceway surface 11 b incontact with the small-diameter-side row of balls 16 so that the maximumwidth dimension between the two ends of the outer ring member 11 and theinner ring member 13 in the axial direction is defined as a unit widthδ1.

Moreover, as shown in FIG. 12, in a state where only thelarge-diameter-side row of balls 15 are attached, the outer ring member11 is shifted in the axial direction so as to make the large-diameterraceway surface 11 a in contact with the large-diameter-side row ofballs 15 so that the maximum width dimension between the two ends of theouter ring member 11 and the inner ring member 13 in the axial directionis defined as a unit width δ2.

Since the axial internal clearance of the large-diameter-side row ofballs 15 is set to be greater than the axial internal clearance of thesmall-diameter-side row of balls 16 by the dimension γ, the followingrelationship is satisfied between the unit width δ1 of thesmall-diameter-side row of balls 16 and the unit width 2 of thelarge-diameter-side row of balls 15.δ1>δ2  (1)

Here, with respect to the row of balls 28 of the ball bearing withsingle raceway 25, for example, the same axial internal clearance as thesmall-diameter-side row of balls 16 of the ball bearing with doubleraceway 10 is prepared.

Next, the following description discusses an assembling method for sucha differential device 1. Upon assembling the differential device 1, theball bearing with double raceway 10 is provisionally assembled so thatthe axial internal clearance is controlled so as to satisfy theexpression (1). The ball bearing with single raceway 25 is alsoprovisionally assembled in the same manner so that the axial internalclearance is controlled.

First, in a state where the front case 3 and the rear case 4 are stillseparated from each other, the outer ring member 11 of the ball bearingwith double raceway 10 is press-inserted to a predetermined position inthe axial direction at which it comes into contact with the step portionformed in the annular wall 27A from the large-diameter opening of thefront case 3. Further, the outer ring member 12 of the ball bearing withsingle raceway 25 is press-inserted to a predetermined position in theaxial direction at which it comes into contact with the step portionformed in the annular wall 27B from the small-diameter opening of thefront case 3.

In a separated manner from these processes, with respect to the unitmember 21 constituted by the inner ring member 13, rows of balls 15 and16 and cages 19 and 20 of the ball bearing with double raceway 10, itsinner ring member 13 is externally fitted to the pinion shaft 7 so thatthe unit member 21 is positioned on the pinion gear side of the shaftportion 9 of the pinion shaft 7.

The pinion shaft 7 to which the unit member 21 has been attached isinserted from its small-diameter side, that is, from the large-diameteropening of the front case 3, so that the balls 18 of thesmall-diameter-side row of balls 16 of the unit member 21 are made incontact with the small-diameter raceway surface 11 b of the outer ringmember 11 so as to roll thereon, and so that the balls 17 of thelarge-diameter-side row of balls 15 of the unit member 21 are fitted tothe large-diameter raceway surface 11 a of the outer ring member 11 (seeFIG. 13).

Next, a plastic spacer 23 is externally fitted to the shaft portion 9 ofthe pinion shaft 7 from the small-diameter opening of the front case 3.Successively, with respect to the unit member constituted by the innerring member 14 of the ball bearing with single raceway 25, the row ofballs 28 and the cage 32, its inner ring member 14 is externally fittedand inserted to the shaft portion 9 of the pinion shaft 7 from thesmall-diameter opening of the front case 3 so that the row of balls 28of the unit member 22 are fitted to the outer ring raceway surface 12 aof the outer ring member 12.

Thereafter, the shielding plate 37 is externally fitted to the shaftportion 9 of the pinion shaft 7 from the small-diameter opening of thefront case 3 so that the trunk unit 44 of the companion flange 43 isspline-fitted to the shaft portion 9 so that its end face is made incontact with the shielding plate 37. Then, the oil seal 46 is attachedthereto and the seal protective cup 47 is attached to the small-diameteropening of the front case 3. Successively, a nut 49 is engaged with thethread portion 48 of the shaft portion 9 so that a predeterminedpre-load is applied to the balls 17 and 18 of the unit member 21 of theball bearing with double raceway 10, as well as to the balls 30 in theunit member of the ball bearing with single raceway 25.

In other words, since the nut 49 is engaged with the thread portion 48,the inner ring member 13 of the ball bearing with double raceway 10 andthe inner ring 14 of the ball bearing with single raceway 25 aresandwiched in the axial direction by the end face of the pinion gear 6and the end face of the companion flange 43 so that a predeterminedpre-load is applied to the balls 17 and 18 of the ball bearing withdouble raceway 10 as well as to the balls 30 of the ball bearing withsingle raceway 25, through the shielding plate 37 and the plastic spacer23.

Here, in the state in which the pre-load has been applied, supposingthat the axial internal clearance of the large-diameter-side row ofballs 15 of the ball bearing with double raceway is A, that the axialinternal clearance of the small-diameter-side row of balls 16 is B andthat the axial internal clearance of the row of balls 28 of the ballbearing with single raceway 25 is C, for example, the followingequations are satisfied:A=+10 [μm] (positive clearance)B=−30 [μm] (negative clearance)C=−30 [μm] (negative clearance)Here, the values are shown as examples, and the present invention is notlimited to these.

In the differential device 1 having the arrangement, lubricating oil isstored inside the differential case 2 so as to be maintained at a levelL in a driving-stop state. The oil is splashed up as the ring gear 8rotates upon driving so that the oil is directed and supplied over theball bearings with double raceway 10 and the ball bearing with singleraceway 25 through the oil circulating path 40 inside the front case 3to lubricate the ball bearings with double race way 10 and the ballbearing with single raceway 25, and is again circulated through theinside of the differential case 2.

In this manner, among the rows of balls 15 and 16 in the ball bearingwith double raceway 10, the axial internal clearance between thelarge-diameter-side row of balls 15 placed on the pinion gear side thatis subjected to a greater load and the raceway surfaces 11 a and 13 athereof is made greater than the axial internal clearance between thesmall-diameter-side row of balls 16 placed on the anti-pinion gear sidethat is subjected to a smaller load and the raceway surfaces 11 b and 13b thereof by a dimension y. Therefore, in a state where a pre-load isapplied, the axial internal clearance A of the large-diameter-side rowof balls 15 forms a positive clearance, and the axial internal clearanceB of the small-diameter-side row of balls 16 forms a negative clearance.Consequently, upon imposing a load on the rows of balls 15 and 16, aradial load and an axial load are first supported by the row of balls 16placed on the anti-pinion gear side that is subjected to a smaller load,while a radial load is mainly supported by the row of balls 15 placed onthe pinion gear side that is subjected to a greater load. Therefore, theimposed load is shared by the row of balls 15 placed on the pinion gearside and the row of balls 16 placed on the anti-pinion gear side, andthe lives of the respective rows of balls 15 and 16 are averaged so thatthe life of the entire system of the ball bearing with double raceway 10is lengthened.

Since the large-diameter-side row of balls 15 of the ball bearing withdouble raceway 10 is not subjected to a great load, it is not necessaryto increase the diameter of the large-diameter-side row of balls 15 sothat it becomes possible to provide a small-size device.

Since the axial internal clearance of the row of balls 28 of the ballbearing with single raceway 25 is made virtually equal in the size tothe axial internal clearance of the small-diameter-side row of balls 16of the ball bearing with double raceway 10, a load is exerted on therows of balls 16 and 28 in a well-balanced manner so that it becomespossible to further improve the system life.

In the pinion-shaft-supporting bearing device of the present embodiment,the ball bearing with double raceway 10, which has a smaller frictionalresistance, is used as a ball bearing on the pinion bear side that issubjected to a greater load as compared to the anti-pinion gear side.Thus, in comparison with the conventional tapered roller bearing, therotary torque is reduced, thereby making it possible to improve theefficiency of the differential device 1. Further, not a ball bearingwith single raceway, but a ball bearing with double raceway is used sothat the load capacity is increased as compared to the ball bearing withsingle raceway, thereby providing sufficient supporting rigidity.

With respect to the ball bearing with double raceway 10, the angularball bearing of the tandem type in which the pitch circle diameter D1 ofthe large-diameter-side row of balls 15 on the pinion gear side is madegreater than the pitch circle diameter D2 of the small-diameter-side rowof balls 16 is used; therefore, in the case when the balls 17 and 18 ofthe two rows have the same diameter, the number of the balls 17 on thelarge-diameter-side row of balls 15 on the pinion gear side can beincreased as compared to the number of the balls 18 on thesmall-diameter-side row of balls 16, with the result that the ballbearing with double raceway 10 is allowed to withstand a greater load.

Here, the ball bearing 25 on the anti-pinion gear side is not limited bythe angular ball bearing with single raceway. For example, a tandem typeangular ball bearing with double raceway in which the pitch circlediameter of the row of balls on the anti-pinion bear side is madegreater than the pitch circle diameter of the row of balls on the piniongear side, or a tapered roller bearing, which forms a back-to-backduplex bearing in cooperation with a ball bearing with double raceway10, may be used.

FIGS. 14, 15, 16A and 16B show modified examples of the presentinvention. The ball bearings with double raceway 10 and 25 in theembodiment are prepared as an oil lubricating type. In contrast, thebearing to be used in the differential device 1 in these modifiedembodiments is prepared as a grease lubricating type. Therefore, no oilcirculating path 40, shown in FIG. 1, is installed in the differentialcase 2.

As shown in FIGS. 14 and 15, the pinion-shaft-supporting bearing deviceof the present modified example uses a tandem-type angular ball bearingwith double raceway as the ball bearing with double raceway 10 on thepinion gear side, and also uses an angular ball bearing with singleraceway as the ball bearing with single raceway on the anti-pinion gearside 25, with grease G being injected between the ball bearing withdouble raceway 10 and the ball bearing with single raceway 25.

The ball bearing with double raceway 10 is constituted by an outer ringmember 11 having a pair of outer ring raceway surfaces 11 a and 11 bthat are separated from each other in the axis direction, an inner ringmember 13 having a pair of inner ring raceway surfaces 13 a and 13 b andtwo rows of balls 15 and 16 that are held by respective cages 19 and 20in the circumferential direction so as to be evenly distributed.

The ball bearing with single raceway 25 is constituted by an outer ringmember 12 having an outer ring raceway surface 12 a, an inner ringmember 14 having an inner ring raceway surface 14 a and a row of balls28 that are held by a cage 32 so as to be evenly distributed in thecircumferential direction.

Seal members 50 and 51 are placed on the pinion gear side end of theball bearing with double raceway 10 and the anti-pinion gear side end ofthe ball bearing with single raceway 25. Grease G is injected into a gapbetween the ball bearing with double raceway 10 and the ball bearingwith single race way 25, and tightly sealed therein by these sealmembers 50 and 51.

With respect to the ball bearing with double raceway 10, the axialinternal clearance is controlled so as to satisfy the relationshiprepresented by the expression (1). Moreover, the axial internalclearance of the ball bearing with single raceway 25 is set to have thesame axial internal clearance as that of the small-diameter-side row ofballs 16 side of the ball bearing with double raceway 10.

With respect to the seal member 50 placed on the pinion gear side end ofthe ball bearing with double raceway 10, a type of seal referred to asan oil seal is used, and with respect to the seal member 51 that isplaced on the anti-pinion gear side end of the bearing ball with singleraceway 25, a type of a seal referred to as a bearing seal is used.

As shown in FIGS. 16A and 16B, the respective seal members 50 and 51 areformed by curing and bonding elastic members 54 and 55 such as rubber torespective ring-shaped core metal parts 52 and 53. Here, lip portions 56and 57, which are made in contact with the elastic members 54 and 55with a predetermined binding force to the inner ring members 13 and 14,are formed on the elastic members 54 and 55.

The lip portion 56 of the seal member 50 mainly prevents gear oil fromflowing therein, and the lip portion 57 of the seal member 51 mainlyprevents sewage and foreign matters from flowing therein from theoutside of the bearing.

The seal member 50 allows the spring 58 to forcefully press the lipportion 56 onto the inner ring member 13; thus, the sealing property isreadily improved so that it is possible to positively prevent oil fromentering the inside of the bearing.

The seal member 51 is designed so that the inner diameter of the lipportion 57 is made smaller than the outer diameter of the shoulderportion of the inner ring member 14 by a predetermined dimension; thus,this dimensional difference makes the lip portion 57 in contact with theinner ring member 14 with an elastically expanded diameter.

The bearing device is occasionally exposed to temperatures in a range of130° C. to 150° C. For this reason, acrylic rubber, heat resistantacrylic rubber and the like are preferably used as the elastic members54 and 55 of the respective seal members 50 and 51. The heat resistantacrylic rubber is an ethylene-acrylic rubber in which ethylene andacrylic acid ester are bonded to each other as main components of acopolymer composition.

Moreover, with respect to the grease G to be sealed in the bearingdevice, diurea-based grease or ester-based grease that has a goodcompatibility with gear oil is preferably used from the view point ofgood heat resistance. More specific preferable examples thereof include:brand name KNG170 made by NIPPON GREASE CO., LTD. and brand name MultempSB-M made by KYODO YUSHI CO., LTD. KNG170, which uses poly α-olefinmineral oil as a basic oil with diurea being used as a thickener, has anapplication temperature range from −30° C. to 150° C. Multemp, whichuses synthesized hydrocarbon as a basic oil with diurea being used as athickener, has an application temperature range from −40° C. to 200° C.

The other structures are the same as those explained by using FIGS. 7through 13.

The pinion-shaft-supporting bearing device having the arrangement alsomakes it possible to provide the same effects as those shown in FIGS. 7through 13.

Different from the oil lubricating type, the bearing device of thepresent invention, which is prepared as the grease lubricating type,eliminates the necessity of forming an oil directing path and an oilcirculating path inside the differential case 2. Therefore, it ispossible to achieve a small-size and light-weight differential device 1,and since it is also possible to make the pinion-shaft-supportingbearing device less susceptible to adverse effects from foreign matterscontained in the oil in the differential device 1, the bearing life canbe improved.

With respect to the sealed space to be filled with grease G, in additionto ring-shaped spaces between the respective inner and outer rings ofthe ball bearing with double raceway 10 and the ball bearing with singleraceway 25, spaces between the front case 3 and the pinion shaft 7 thatare located between the ball bearing with double raceway 10 and the ballbearing with single raceway 25 are also used. Therefore, it is possibleto sufficiently maintain the amount of grease G used for lubricating theball bearing with double raceway 25 and the ball bearing with singleraceway 10.

With respect to the bearing on the anti-pinion gear side, a tandem-typeangular ball bearing with double raceway and a tapered roller bearingmay be used.

FIGS. 17 and 18 show another modified example of the present invention.

In the present modified example, a bearing unit 60 is used as thepinion-shaft-supporting bearing device. By using this bearing unit 60,the pinion shaft 7 is supported on the front case 3 of the differentialcase 2 so as to freely rotate thereon.

The bearing unit 60 is provided with a ball bearing with double raceway10 that is a tandem-type angular ball bearing with double raceway on thepinion gear side and a ball bearing with single raceway 25 that is anangular ball bearing with single raceway on the anti-pinion gear side.

The ball bearing with double raceway 10 is constituted by an outer ringmember 61, an inner ring member 13 and two rows of balls 15 and 16 thatare held by respective cages 19 and 20. The ball bearing with singleraceway 25 is constituted by an outer ring member 61, an inner ringmember 14 and a row of balls 28 held by a cage 32. A pair of inner ringraceway surfaces 13 a and 13 b are formed on an outer circumferentialface of the inner ring member 13, and an inner ring raceway surface 14 ais formed on the outer circumferential face of the inner ring member 14.Outer ring raceway surfaces 11 a, 11 b and 12 a, which face therespective inner ring raceway surfaces 13 a, 13 b and 14 a in the radialdirection, are formed on the inner circumferential face of the outerring member 61. Both of the inner ring members 13 and 14 are allowed tobutt each other in the axial direction.

The bearing unit 60 is provided with seal members 50 and 51 on two sidesthereof in the axial direction. These seal members 50 and 51 seal greaseG inside the ring shaped spaces that are located between the outer ringmember 61 and the two inner ring members 13 and 14.

The rows of balls 15 and 16 of the ball bearing with double raceway 10are controlled in the axial inner clearances thereof so as to satisfythe relationship of the expression (1). The row of balls 28 of the ballbearing with single raceway 25 is also set to have the same axial innerinternal clearance as the small-diameter-side row of balls 16 of theball bearing with double raceway 10.

The following description discusses an assembling method for thedifferential device 1. With respect to the bearing unit 60, uponmanufacturing, the inner ring members 13 and 14, the outer ring member61 and the rows of balls 15, 16 and 28 that are held by the cages 19, 20and 32 are properly assembled so that an accurate pre-load is appliedthereto.

The bearing unit 60 is assembled onto the pinion shaft 7 from the driveshaft side, with the inner ring member 13 being externally fitted andinserted to the large-diameter portion of the pinion shaft 7 and theinner ring member 14 being externally fitted and inserted to themiddle-diameter portion thereof. Next, the companion flange 43 isspline-fitted to the small-diameter portion of the pinion shaft 7, andthe end portion on the drive shaft side of the shaft portion 9 of thepinion shaft 7 is deformed outward in the radial direction so that thisportion is caulked onto the companion flange 43. A caulked portion 91 isformed on the shaft portion 9 through these processes so that thebearing unit 60 is sandwiched by the pinion gear 6 and the trunk portion44 of the companion flange 43; thus, a pre-load is applied.

Moreover, the flange 62 formed on the outer ring member 61 is made incontact with the outer face of the front case 3, and a bolt 64 isinserted through the flange 62, and connected to the front case 3 sothat the bearing unit 60 is secured to the front case 3.

A packing 63 that prevents oil of the differential device 1 from leakingis interpolated between the outer circumferential portion of the outerring member 61 and the inner wall face of the attaching opening of thefront case 3.

The other structures are the same as those of examples shown in FIGS. 7through 13.

The pinion-shaft-supporting bearing device having the arrangement makesit possible to provide the same effects as those of examples shown inFIGS. 15 and 16.

Moreover, since the bearing unit formed by using a single outer ringmember 61 is used as a bearing that supports the pinion shaft 7 on thedifferential case 2 so as to freely rotate thereon, the pre-loadadjustment is accurately carried out in the manufacturing processes ofthe bearing unit 60. Therefore, it becomes possible to eliminate thenecessity of conducting pre-load adjusting operations at the time ofassembling the differential device 1. Thus, it becomes possible toreduce the number of assembling processes of the differential device 1,and consequently to improve the assembling property.

FIG. 19 further shows another modified example of the present invention.FIG. 19 shows a cross-sectional view of the pinion-shaft-supportingbearing device of a differential device 1 in the present modifiedexample.

In the present modified example, the trunk portion 44 of the companionflange 43 is used as the inner ring member of the ball bearing withsingle raceway 25 on the anti-pinion gear side of the shaft-receivingunit 60.

In other words, an inner ring raceway surface 14 a is formed on theouter circumferential face of the trunk portion 44 of the companionflange 43. Thus, the ball bearing with single raceway 25 is constitutedby the companion flange 43, the outer ring member 61 and the row ofballs 28 that are held by the cage 32.

The rows of balls 15 and 16 of the ball bearing with double raceway 10are controlled in their axial internal clearances so as to satisfy therelationship of the expression (1). Moreover, with respect to the row ofballs 28 of the ball bearing with single raceway 25 also, for example,the same axial internal clearance as that of the small-diameter-side rowof balls 16 of the ball bearing with double raceway 10 is prepared.

With respect to the assembling processes of the bearing unit 60, theinner ring member 13 is press-inserted into the pinion shaft 7 from thedrive shaft side, and the companion flange 43 is spline-fitted to thepinion shaft 7, with the nut 49 being fastened to the drive-shaft-sideend of the pinion shaft 7, so that a pre-load is applied onto thebearing unit 60.

The bearing unit 60, assembled as described above, is secured byinserting a bolt 64 into the flange 62 to be fastened to the front case3, with the flange 62 formed on the outer ring member 61 being made incontact with the outer face of the front case 3.

Here, the other structures are the same as those of examples shown inFIGS. 17 and 18.

The pinion-shaft-supporting bearing device having the arrangement alsomakes it possible to provide the same effects as those of examples shownin FIGS. 17 and 18.

In the present modified example, since the trunk portion 44 of thecompanion flange 43 is used as the inner ring member of the ball bearing25 with single raceway, it becomes possible to reduce the number ofparts in comparison with a conventional differential device, andconsequently to reduce the manufacturing costs.

FIG. 20 shows still another modified example of the present invention.

FIG. 20 shows a cross-sectional view of a pinion-shaft-supportingbearing device of a differential device in accordance with the presentmodified example.

In the present modified example, the trunk 44 of the companion flange 43is used as the inner ring member of the bearing with single raceway 25on the anti-pinion gear side of the bearing unit 60, and the shaftportion 9 of the pinion shaft 7 is used as the inner ring member of theball bearing with double raceway 10 on the pinion bear side.

An inner ring raceway surface 14 a is formed on the outercircumferential face of the trunk portion 44 of the companion flange 43.The ball bearing with single raceway 25 is constituted by a companionflange 43, an outer ring member 61 and a row of balls 28 that are heldby a cage 32.

A pair of inner-ring raceway surfaces 13 a and 13 b, each having alarger diameter on the pinion gear side, which are separated from eachother in the axial direction, are formed on the outer circumferentialface of the shaft portion 9 of the pinion shaft 7. The rolling bearingwith double raceway 10 is constituted by a pinion shaft 7, an outer ringmember 61 and rows of balls 15 and 16 that are held by cages 19 and 20.

The ball bearing with double raceway 10 is controlled in its axialinternal clearance so as to satisfy the relationship of the expression(1). Moreover, with respect to the row of balls 28 of the ball bearingwith single raceway 25 also, for example, the same axial internalclearance as that of the small-diameter-side row of balls 16 of the ballbearing with double raceway 10 is prepared.

With respect to the assembling processes of the bearing unit 60, therows of balls 15 and 16 are attached to the inner-ring raceway surfaces13 a and 13 b of the pinion shaft 7 from the drive shaft side, and thecompanion flange 43 is spline-fitted to the pinion shaft 7, with the nut49 being fastened to the drive-shaft-side end of the pinion shaft 7, sothat a pre-load is applied thereon so as to be secured.

Moreover, the flange 62 of the outer ring member 61 is made in contactwith the outer face of the front case 3, and the bolt 64 is insertedinto the flange 62, and fastened to the front case 3.

Here, the other structures are the same as those of examples shown inFIGS. 17 and 18.

The pinion-shaft-supporting bearing device having the arrangement alsomakes it possible to provide the same effects as those of examples shownin FIGS. 17 and 18.

Furthermore, the inner ring of the ball bearing with single raceway 25is integrally formed in the companion flange 43, with the inner ring ofthe ball bearing with double raceway 10 being integrally formed in thepinion shaft 7, so that it becomes possible to reduce the number ofparts, and consequently to further cut the manufacturing costs.

In accordance with the pinion-shaft-supporting bearing device of theembodiments, in the angular ball bearing with double raceway on thepinion gear side, the imposed load is shared by the row of balls placedon the pinion gear side and the row of balls placed on the anti-piniongear side; thus, the lives of the respective rows of balls are averagedso that the life of the entire system of the ball bearing with doubleraceway is lengthened.

INDUSTRIAL APPLICABILITY

The rolling bearing with double raceway of the present invention isdesirably applicable to a differential device or the like that isinstalled in, for example, a vehicle.

1. A ball bearing with double raceway, which rotatably supports a pinionshaft having a pinion gear on one end thereof in an axial direction,comprising: an outer ring member having a large-diameter raceway surfaceand a small-diameter raceway surface that are spaced from each other inthe axial direction; an inner ring member having a large-diameterraceway surface and a small-diameter raceway surface that are spacedfrom each other in the axial direction so as to be respectivelypositioned inside the large-diameter raceway surface and thesmall-diameter raceway surface in a radial direction; alarge-diameter-side row of balls that are interpolated between the twolarge-diameter raceway surfaces; a small-diameter-side row of balls thatare interpolated between the two small-diameter raceway surfaces,wherein internal clearances on the two large-diameter raceway surfacesside as well as on the two small-diameter raceway surfaces side aredesigned to have respectively different sizes in such a manner that uponapplying a load on the pinion shaft, the row of balls on the anti-piniongear side of the two rows of balls is subjected to the load prior to therow of balls on the pinion gear side.
 2. The ball bearing with doubleraceway according to claim 1, wherein a radial internal clearance on theanti-pinion gear side is made smaller than a radial internal clearanceon the pinion gear side.
 3. The ball bearing with double racewayaccording to claim 1, wherein an axial internal clearance on theanti-pinion gear side is made smaller than an axial internal clearanceon the pinion gear side.
 4. The ball bearing with double racewayaccording to claim 1, wherein balls that respectively constitute the rowof balls on the pinion gear side and the row of balls on the anti-piniongear side have virtually the same diameter so that the row of balls onthe pinion gear side have a pitch circle diameter greater than the pitchcircle diameter of the row of balls on the anti-pinion gear side.
 5. Apinion-shaft-supporting bearing device comprising: a plurality ofrolling bearings that support a pinion shaft having a pinion gear at oneend in an axial direction at predetermined positions on the pinion gearside and the anti-pinion gear side, wherein at least the rolling bearingon the pinion gear side is prepared as a ball bearing with doubleraceway that comprises: an outer ring member having a large-diameterraceway surface and a small-diameter raceway surface that are placed ina separate manner from each other in the axial direction; an inner ringmember having a large-diameter raceway surface and a small-diameterraceway surface that are placed in a separate manner from each other inthe axial direction; a large-diameter-side row of balls and asmall-diameter-side row of balls that are respectively interpolatedbetween the raceway surfaces of the outer ring member as well as betweenthe raceway surfaces of the inner ring member, the ball bearing withdouble raceway being arranged so that internal clearances on the twolarge-diameter raceway surfaces side as well as on the twosmall-diameter raceway surfaces side are designed to have respectivelydifferent sizes in such a manner that upon applying a load on the pinionshaft, the row of balls on the anti-pinion gear side of the two rows ofballs is subjected to the load prior to the row of balls on the piniongear side.
 6. The pinion-shaft-supporting bearing device according toclaim 5, wherein the large-diameter-side row of balls are placed on thepinion gear side and the small-diameter-side row of balls are placed onthe anti-pinion gear side, and a radial internal clearance on theanti-pinion gear side is made smaller than a radial internal clearanceon the pinion gear side.
 7. The pinion-shaft-supporting bearing deviceaccording to claim 5, wherein the large-diameter-side row of balls areplaced on the pinion gear side and the small-diameter-side row of ballsare placed on the anti-pinion gear side, and an axial internal clearanceon the anti-pinion gear side is made smaller than an axial internalclearance on the pinion gear side.
 8. A pinion-shaft-supporting bearingdevice comprising: a plurality of rolling bearings that rotatablysupport a pinion shaft having a pinion gear at one end in an axialdirection at predetermined positions on the pinion gear side and theanti-pinion gear side, wherein the rolling bearing on the pinion gearside is prepared as a ball bearing with double raceway that comprises:an outer ring member having a large-diameter raceway surface and asmall-diameter raceway surface that are spaced from each other in theaxial direction; an inner ring member having a large-diameter racewaysurface and a small-diameter raceway surface that are spaced from eachother in the axial direction; and a large-diameter-side row of balls anda small-diameter-side row of balls that are respectively interpolatedbetween the raceway surfaces of the outer ring members as well asbetween the raceway surfaces of the inner ring members, and the rollingbearing on the anti-pinion gear side is prepared as a ball bearing withsingle raceway that comprises: an outer ring member, an inner ringmember and a single row of balls that are interpolated between an outerring raceway surface formed on the outer ring member and an inner ringraceway surface formed on the inner ring member, the ball bearing withdouble raceway being arranged so that an internal clearance on theanti-pinion gear side is made smaller than an internal clearance on thepinion gear side in such a manner that upon applying a load on thepinion shaft, the row of balls on the anti-pinion gear side of the tworows of balls is subjected to the load prior to the row of balls on thepinion gear side, the ball bearing with single raceway being arranged sothat an internal clearance in the ball bearing with single raceway beingmade virtually equal to an internal clearance on the anti-pinion side inthe ball bearing with double raceway.
 9. The pinion-shaft-supportingbearing device according to claim 8, wherein a radial internal clearanceon the anti-pinion gear side in the ball bearing with double raceway ismade smaller than a radial internal clearance on the pinion gear side,and a radial internal clearance in the ball bearing with single racewayis made virtually equal to a radial internal clearance on theanti-pinion side in the ball bearing with double raceway.
 10. Thepinion-shaft-supporting bearing device according to claim 8, wherein anaxial internal clearance on the anti-pinion gear side in the ballbearing with double raceway is made smaller than an axial internalclearance on the pinion gear side, and an axial internal clearance inthe ball bearing with single raceway is made virtually equal to an axialinternal clearance on the anti-pinion side in the ball bearing withdouble raceway.